(a) Field
The present invention relates to a method and apparatus for controlling signal transmission of a wireless communication system. More particularly, the present invention relates to a method and apparatus for controlling signal transmission that can save power and reduce interference in a wireless communication system.
(b) Description of the Related Art
In order to increase capacity of a network, by overlappingly disposing cells of different sizes using the same frequency band such as a low power small remote radio head (RRH) cell, a pico cell, a relay, and a femto cell, heterogeneous network technology for enlarging a cell capacity per unit area and for improving QoS of a terminal that is positioned at a cell boundary area is emerging, along with a wireless communication system and a wireless access service network for continuity of a multimedia service.
In order to enlarge mobile traffic capacity of a network in addition to a macro cell base station, at a home, a school, a company, and a hot spot region, a base station of a small-sized cell such as a pico cell and a femto cell is installed, cell coverage for securing reliability and enhancing performance of wireless communication in a railroad and an express highway is extended, an additional base station for guaranteeing mobility is installed, and in order to solve a weak radio area, a relay is installed.
However, there is a drawback that enlargement of various types of base stations corresponding to the number of cells that is increased with enlargement of capacity of a network for satisfying an explosively increasing wireless data service increases interference between cells as well as power consumption.
At a time zone and location where a communication amount of an actual user is high, user traffic is concentrated. At a company, a school, or a home, due to a user's movement, user traffic may be concentrated, very little traffic may occur, or traffic may not occur, and at a park or a leisure life region, concentration, absence, and distribution of traffic may occur according to a user moving time. In this way, a situation in which mobile traffic does not occur or in which a consumption amount of mobile traffic is much less may sequentially frequently occur.
However, a base station of an existing wireless communication system always periodically transmits a control signal regardless of whether a terminal is connected, a state of a connected terminal, or a demand amount of user traffic, a terminal acquires synchronization or system information such as a preamble, a common pilot, a beacon signal, and a reference signal for measuring a quality state of a wireless signal of a downlink, and a downlink control channel signal for acquiring system information and information of a corresponding transmitting frame or subframe correspond to the control signal. Thereby, even when a terminal that is connected to the base station does not exist or is in an idle state, or even when mobile traffic does not exist or even when a demand amount of mobile traffic is small, a reference signal of a downlink control channel signal and a pilot signal has periodicity, and as the reference signal is continuously transmitted by a base station without distinction, there is a drawback that power consumption of a base station continuously occurs.
Even if traffic to transmit to a downlink does not exist for a predetermined time regardless of whether a terminal that is connected to the base station exists or a service connection state, in order to transmit such a control signal from the base station to a downlink, for operation of a modulation apparatus of a physical (PHY) layer using a modulation method such as a medium access control (MAC) layer and orthogonal frequency division multiple access (OFDMA), power is requested and power of an RF apparatus for transmitting by wireless is always necessary. Further, transmission of such a control signal may interfere with an adjacent cell.
Therefore, in the wireless communication system, for a wireless frame interval in which transmission of a reference signal such as a downlink control channel signal and a pilot signal is continued, by controlling transmission of a wireless signal as needed, unnecessary power consumption is reduced, and by reducing interference between neighboring or overlapped base stations, it is necessary to reduce transmission power of a neighboring base station such as that caused by unnecessary retransmission.